linux-kernel - Re: [PATCH v2 1/7] ACPI: Add CONFIG_HOTPLUG

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Date:	Fri, 11 May 2012 08:15:26 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	Toshi Kani <toshi.kani@...com>
CC:	lenb@...nel.org, linux-acpi@...r.kernel.org, bhelgaas@...gle.com,
	shuahkhan@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/7] ACPI: Add CONFIG_HOTPLUG_OST option

On 05/11/2012 02:20 AM, Toshi Kani wrote:
> On Fri, 2012-05-11 at 01:43 +0800, Jiang Liu wrote:
>> On 05/11/2012 01:26 AM, Toshi Kani wrote:
>>> On Fri, 2012-05-11 at 00:40 +0800, Jiang Liu wrote:
>>>> On 05/09/2012 04:12 AM, Toshi Kani wrote:
>>>>> Added CONFIG_ACPI_HOTPLUG_OPT option. When this config option is disabled,
>>>>> this patchset has no effect on the platform. This option is disabled by
>>>>> default. The dependency list assures consistent behavior among CPU, memory
>>>>> and container hotplug operations with regarding the _OST support.
>>>> Seems also need to enhance the acpiphp driver for PCI hotplug operations too.
>>>> acpiphp driver is also based on the ACPI device hotplug model.
>>>
>>> Good question.  ACPI PCI hotplug is a legacy method, which is being
>>> replaced by PCI native hotplug.  I expect PCI native hotplug will be
>>> used for any platforms supporting PCI-E.  Since this _OST support is
>>> targeted for new platforms (as _OST is not supported on the current
>>> platforms), I thought that it would be prudent to avoid changing PCI
>>> hotplug code for this.
>> You are right, acpiphp is legacy method. But it may also be used to support
>> some cases which can't be supported by the pciehp driver.
>> For example, we have a PCIe system which needs to run acpiphp and pciehp
>> concurrently. The pciehp driver is used to manage hot-pluggable PCIe slot,
>> and the acpiphp driver is used to migrate downstream ports among virtual 
>> PCIe switches of an MR-IOV switch. It would be great if we could enable 
>> _OST for acpiphp too.
>>
>> To be honest, our BIOS doesn't provide _OST for acpiphp yet, so we could
>> enhance acpiphp driver in future when a system really needing that feature
>> appears.
> 
> Interesting.  In such case, I am willing to change acpiphp, but I am
> afraid that I do not have access to platforms with ACPI PCI hotplug
> support.  My test systems are all PCI-E based.  So, it would be great if
> you could enhance acpiphp when you need it.
Sure, I will enhance it based on your work when needed.
Thanks!
-Gerry

> 
> 
> Thanks!
> -Toshi
> 

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